This invention relates to apparatus for charging finely ground particulate materials such as potent animal feed additives or drugs into bins, e.g., very small or "micro" bins. Feed additives such as drugs and/or vitamin concentrates are typically finely ground particulate material received in bag- or box-type containers. When these are to be weighed out, e.g., to be mixed or to be mixed with feed, a container of the finely ground material is placed on a platform and weighed, and then dumped into a bin. This creates two potential difficulties. One difficulty is the exposure to workmen of the potent fine dust that tends to billow up into the atmosphere with dumping and consequential air displacement, to be possibly breathed by the operator and others. In fact, OSHA requirements now restrict such exposure of workers. Conventional equipment often employs a ventilation stack system with filters at the outlet in efforts to limit dissemination of the dust. The second difficulty is the FDA requirement of accounting for all of the potent chemicals such as drugs and vitamin concentrates. Loss of particulate material into the atmosphere, or clinging to equipment or filters in a discharge stack, is almost impossible to prevent using present equipment, and thus almost impossible to fully account for to the FDA. Such losses are also costly.